J.E. Isles, 118 Liverpool Road, Watford, Herts. WD1 8DN Tel; WAtford (0923) D.R.B. Saw, 12 Taylor Road, Aylesbury, Bucks.

Transcription

1 BEITISH ASTRONOMICAL ASSOCIATION VARIABLE STAR SECTION CIRCULAR No. 23 OFFICERS OF THE V.S.S. Director; Secretary; J.E. Isles, 118 Liverpool Road, Watford, Herts. WD1 8DN Tel; WAtford (0923) D.R.B. Saw, 12 Taylor Road, Aylesbury, Bucks. HP21 8DR Chart Curator; S.J. Anderson, 20 Bloomfield Avenue, Luton, Beds. LU2 OPS Tel; Luton (0582) BINOCULAR GROUP Co-ordinator; D.A. Pickup, 38 Brockwood Avenue, Penicuik. Midlothian. EK26 9AN Tel; Penicuik Asst. Co-ordinator; J).L Smith, 11 Lerryn Road, Gosport, Hants. P013 OYG Tel; Fareham (032 92) *+677 Recorder; A.E.J. Forno, 92 Crockford Park Road, Addlestone, Surrey. KT15 2LR Tel; Weybridge (0932) kb66o ECLIPSING BINARY PROJECT Co-ordinator; Predictions? J.E. Isles J.C. Smith, 18 St. James Close, Hanslope, Bucks NOVA SEARCH PROJECT Co-ordinator; C.V. Borzelli, 12 Corbin Avenue, Jersey Citv. N.J , U.S.A. Hill ll lll NOVA CYGNI BACK PAGE 1III HI HI

2 BRITISH ASTRONOMICAL ASSOCIATION: VARIABLE STAR SECTION CIRCULAR No ? SEPTEMBER VSS Circulars. Members are reminded that SAEs for Circulars should be sent to the Director: if they are sent to anyone else you may miss a Circular, ifcie Director is grateful to those few members who have sent additional stamps to cover increases in postage since SAEs were sent it. We have no means of knowing which oversea members require the Circulars 5 therefore, from now on, members outside the UK who wish to receive them are asked to send the Director a batch of (unstamped) addressed envelopes, of at least 22cm x 8cm dimensions, in which Circulars will be despatched. Write "LAST SAE" on one of the envelopes, so that you will know when you have to send more. The only exception to this arrangement will be those overseas groups with whom we exchange publications they will continue to receive VSS Circulars automatically. VSS MEETING1 - CHESTER, 1975 September 13. Chester Astronomical Society will be our hosts at the first VSS meeting to be held for eight years, on Saturday September 13 (not as stated in the last Circular) at Kingsway High School, whose location is indicated on the enclosed finder chart*. The meeting will run from 2 pm to 6 pm and probable speakers include: D.A. Pickup: The VSS Binocular Group, and Fourier Analysis of Light Curves. P.W. Hornby: The Eclipsing Binary Programme. O'.A. Bailey: Dwarf Novae as Binary Systems. S.J. Anderson: The British Photographic Sky Patrol. S.J. Hynes: "Clouds of Light". J.E. Isles: Progress of the Variable Star Section. I.D. Howarth: surprise item. Refreshments will be available, but so that the organisers can have sowb idea of the numbers concerned, those who will require them are asked to write to Richard Baum, 25 Whitchurch Road, Chester CH3 5QA. If you do not write you may not be served! Those requiring overnight accomodation may also contact Mr. Baum (Tel: Chester 35^^+). There will, in addition, be an exhibition of work done by members of the Chester society and of VSS light curves. Any VSS members who wish to exhibit something may bring the material along, or if unable to attend, send it to the Director. 197*f observations. The following statistics are based mainly on tabulations prepared by the Secretary, Doug Saw, for the main programme, and the Recorder of the Binocular Group, Alan Forno. The Binocular" Group figures include about 800 observations of stars not at present included in the official programmej such observations will not be counted next year. Non-programme observations have not been counted in the main programme totals. A total of ^-2,731 observations has been reported, this being nearly double the 1973 total and four times the 1972 total. This year's increase is largely due to our "merger" with the Binocular Sky Society and it is likely that any increase in 1975 will not be so great. However, coping with these observations still presents the Section's officers and helpers with a formidable task. O.J. Knox was once again the leading telescopic observer, and made probably the largest contribution in terms of man-hours. The Director was sorry to hear that recently he has been unwell but is sure that members will be pleased to know that Mr. Knox is getting back into harness and has resumed observing. D. Hufton bagged the highest total overall, 3,875 observations, while several other members reported formidable totals and there are about two dozen observers who maybe considered really active for the Section.

3 2 / The Secretary reports that once again the early morning observations by Knox were invaluable in extending the light curves of many stars, while the positive observations of faint stars by Paterson, and also Howarth, were extremely useful, There was a good response to the RV Tauri project; the Swiss observers have reported their Results directly to the VSS and are included in the table, but it is known that the French observers have secured large numbers of results and it is clear that the final report, which the Dutch group are to publish, will be an extremely valuable document. Coverage of the programme stars was very uneven; the four most popular objects (Gamma Gas, Rho Cas, R CrB, SS Cyg) were each observed over 1000 times and it is suspected that some observers may be using these bright objects to increase their totals and position in the VSS hit parade. On the other hand, some of the Mira stars have been sadly neglected, in particular V Cam, W CrB, S Cyg and R Hya. Listed on the following pages are the numbers of results reported by each of the 55 observers who secured 100 or more estimates, and the totals (with the numbers of observers in brackets) for each star on the main and binocular programmes. More observations are required, not only of those stars for which the totals are low, but also for those stars on which only a few members are working. However, attention is drawn to the fact that the stars in list (B) are no longer in the programme and any further observations of them will be neither used by the VSS nor counted in future statistics. The stars in list (A) are common to the main and binocular programmes, and they have been credited to the observers in either the main programme column or the Binocular Group column, depending on whether they were reported to the Secretary or the Recorder of the Binocular Group, The figures do not therefore indicate the true proportions of telescopic and binocular work by each observer, and it is intended to rectify this point in next year*s statistics. Main Binocular Eclipsing Programme Group Binaries Total. D. Hufton * O.J. Knox 3, T. Brelstaff 1-+3½ M.D. Taylor I.A. Middlemist 5-: J.A. Bailey L.R. Matthews 12)+2 3-3l 1732 P.W. Hornby Δ.Κ. Porter 123½ R.A.H. Paterson D.P. Griffin 10οί B.J. Beasley I.D. Howarth D.R.B. Saw G-. Broadbent N. Reid * _ 913 E.J.W. West 218 6I ?3 D.A. Rothery G.M. Hurst C.R. Munford 63o () P.A. Moore G.J. Kirby r> A. Gardner ~ J.D. Sharklin y D.L. Young

4 Main Binocular Eclipsing Programme Group Binaries Total K. Locher _ '0m μ Λ Λ Ν. Richardson Α.Β. Scott D. Btthme ^ S.F. Burch 3*+6 3 b 6 - Mrs. M. Hoenig ^. 3^3-3^3 ΛΛη W.E. Pennell 293 M* α,λγΐ D. Churchill 271 l6-287 A. Maudsley 178 k *+ D.M. Swain K. Sturdy S. Taylor R.J. Livesey 130 M J.W. Mason r?5-175 D. Miles R.D. Pickard 9 1 b? M.Jc Gainsford l*+5 l b 5 F.D. Chesterfield i o.o> A )*. 12 _ lmf H.-.W.S. Smith 1 ¾ S,R. Hsathcote mm E H Collinson R.J. Goddon. m m R. Diethelm mm GLW.,E, Be airman C. Henshav mm G.H. Spalding 116 <* mm 11.6 R.L. Lyon 10ό - IGo M. Peel * I.A. Robinson B.N o Marchant 100 mm Observers 1228 ^ Totals 2**32k ^ 561 U-2731 CA) Stars common to main and binocular programmes R And 3 ½. (25) Omi Cet 220 (20) R Hya 63 (12) R Aql 288 (21) Π CrB 15^8 0*7) ϋ Mon 288 (25) CO Aur 372 (32) s GrB 228 (16 ) U Ori 23½ (24-j /)1.0 S V Boo 339 (25) w CrB 13>+ (15) R Set 685 (4 -ο,ί. X Cam 203 (1>+) R Cyg 233 (19) R Ser p4-4- V (20) XX. Cam 255 (IV) w Cyg 873 (38) T UMa 3-lJ in (12) Gam Gas 1168.(26) Chi Cyg 324- (20) V V ul 0/ Rho Cas (39) AC Her 36U- (2V) (B) Stars now dropped from the main programme R Ari.59 (5) S Cep 29 (3) w Lyr Ϊ1 (2) R Aur CD φ m* Cep 219 (15) R Peg f t (1) HX X Aur 159 (13) U Cyg 168 (11) R Per n Q (If) I 7 R Boo 78 (½) s Del 29 (3) R Tri 0 (13) S Boo 22 (2) R Dra 1^3 (9) R UMa λ κ Λ (14-> AF Cam 33 (3) R Gem 95 (9) S UMa n OO (8) R Cas 23 (5) T Her 87 (6) s UMi θ (\ (2) Cas 3.57 (11) U Her 59 M s Vir Cas 96 (5) R Leo 197 (18) HT. Cas 33 (3) R Lyn 22 (3)

5 (C) Other starsi on the main programme RX And (17) SS Her 150 (20) V372 Ori 6f (6) /Υ» y DZ And 106 (6) AH Her 217 (10) V529 Ori 6½ uu Aql 131 (10) SU Lac 22 (½) V566 Ori 56 uw Aql 1 ¾ (11) X Leo 238 (20) CSV Ori 3? RW Aur ½2 (3) AY Lyr 258 (11) Var. No.2 Ori λ ϊ \ ss Aur 50½ EG so Aur b 9 8! ΞΡ Lyr (10) RU Peg 431 (2o) Lyr *3 (10) S Per 279 (22) u Boo 168 (17) RS Oph 263 (16 ) RS Per 213 (16; V Cam bl (8) TT Oph 16 (6) TZ Per (17; z Cam 687 (18) TX Oph 12 (½) UV Per (10) TW Cam 203 (20) UZ Oph 6 (2) m Per 206 s Cas (12) V56½ Oph 10 (3) GK Per uv Cas l6l (8) T Ori if9 Nova Per 197½ 76 (9) e q Cas 5 (½) CN Ori 107 (10) R Sge 73 (12) T CrB 555 (2 b ) CT Ori 100 (1½) WZ See 218 (10) s Cyg 75 (8) cz Ori 118 (10) Nova Sgr 197½ (½) A X 1 Λ S ss Cyg 1077 (33) DY Ori io5 (10) Z Sex li 5 (19) BC cyg 237 (12) GW Ori 21 (3) T Tau 157 (10) BI cyg 260 (11) IU Ori 62 (6) RV Tau ¾ Cl cyg 56 KS Ori 36 (5 ) RY Tau 36 (½) DP Cyg 39 (10) KX Ori 7 (2) SU Tau 273 (19) V36o Cyg 36 (10) LP Ori 70 (6) BW Tau 2 (l) HR Del 223 (1½) MX Ori 56 (6) SU UMa 316 (Ιό) AB Dra 302 (10) NU Ori 97 (6) SW UMa 23½ (11 / U Gem 328 (1 9 ) NV Ori 35 (5) CH UMa 240 SS Gem 199 (22) V359 Ori 6 (2) SN NGC 4 ¾ ½ 19 (½) su Gem 97 (11) V361 Ori 6b (6) (D) Other stars on the Binocular Group programme RS And 17 (6) V CVti 168 (1 ½) RV Cyg 99 (10) SU And 16 (5) Y CVn 231 (1 ½) TT Cyg 97 to; TZ And 37 (8) TU CVn 229 (15) AF Cyg 24-2 u p ; AQ And 77 (9) W CMa 9 (3) CH Cyg 382 U6J BZ And 35 WZ Cas 189 (12) V46o Cyg 93 CIO ) - y A< 69 (9) V377 Cas 212 (9) V973 Cyg 6 u) Vb50 Aql 102 9) V391 Cas 97 (9) V1351 Cyg 5 U) V1293 Aql 92 V393 Cas 123 (10) P Cyg ) CSV 10l8½9 Aql 88 Vb65 Cas 205 (16) CSV 8232 Cyg 23 (3) UU Aur 298 (21) CSV 171 Cas 101 (9) CSV 8307 Cyg 97 (5) AB Aur 118 (8) Wr 162 Cas 168 (13) CSV 8683 Cyg 76 (6) AE Aur 276 (1½) +49 ½329 Cas 66 (½) 28 Cyg 152 (ID NO Aur ½5 (6) W Cep 160 (13) +½ Cyg 95 (4-) Psil Aur 37 (5) RU Cep 71 (8) U Del 307 (28) Aur 76 (½) RW Cep 190 (16 ) EU Del 3½7 (27) RV Boo 29 RX Cep 125 (9) +19 4½ 50 Del 122 (ID RW Boo 30 SS Cep 158 (9) RY Dra b90 (23) RX Boo 89 (12) AR Cep 235 (13) TX Dra l4l (9) UV Boo 131 (12) FZ Cep (3) UW Dra 70 (6) U Cam 5½ (5) NN Cep 7b UX Dra 143 (10) RY Cam 95 (11) Mu Cep 158 (11) VW Dra 87 (8) ST Cam 120 (10) CSV 927 Cep 111 (5) AH Dra 125 (9) UV Cam 120 (11) +59^ 2383 Cep 92 (5) AT Dra 93 (9) UX Cam Cep 101 (5) 69 Dra 102 (8) VZ Cam 126 (8) +8½ Cep 11 (3) TU Gem 53 (10) ZZ Cam 136 (11) 33 Cet 2½ (3) TV Gem 1+6 (1½) Cam 10½ RR CrB 78 (9) WY Gem 139 (1½) X Cnc 89 (10) SW CrB 79 (9) BN Gem 8? (8) RS Cnc 137 (18) T Cyg 163 (12) BQ Gem 5 (9) RT Cnc 30 (8) RU Cyg 28 (5) BU Gem 167 (15)

6 (D) continued; DW Gem IS Gem NQ Gem X Her ST Her SX Her UW Her IQ Her OP Her V566 Her g Her U Hya SX Lac CSV 8775 Lac CSV Lac RX Lep % 14 % $ lb (3) (2) (18 ) (8),(4) (1 2 ) (lb ) (5) (17) S Mon RV Mon SX Mon V505 Mon X Oph V20b8 Oph W Ori BL Ori BQ Ori CK Ori b-7 Ori AG Peg GO Peg X Per SU Per AD Per ? b-2 38 (b-) (1 ) (1 ) (2) (6) (3) (9) (8) (20) (6) (16 ) (8) (?) \. Y Tau \ TT Tau \ BU Tau \CE Tau CSV 6bbB Tau ^b-3 Tau W Tri Z UMa RY UMa ST UMa TV UMa VW UMa VY UMa V UMi R Vir RX Vir 60 3? (9) (1 1 ) (6) (2) (4) (23) (20) (10 ) (bo (2) (4) (lb ) (1 2 ) (1 1 ) 329 (10 ) (5) (4) (3) 26 J 3 Y Lyn (8) (2) KK Per 30 (8) SS Vir 7 SV Lyn PR Per (3) 28 (8) SW Vir 4 (2 ) CSV Lyn 24 (3) Z Psc 17 (3) BK Vir 3 R Lyr 320 (1 ) (15) TV Psc 67 V Vul 3 (2) XY Lyr Del^ Lyr 98 (8) TX Psc (9) S Set 65 (9) 197m- light--curves. The following notes on main programme stars in constellations And - Cyg, plus AB Dra, are based on the plots prepared by the Secretary from observations reported to him. They will be continued m a future Circular. R And? Fell from 12.3 on Jan 8 to lb-.l on Feb 22. Unobserved until Jun9, 13.0; rose to max (6.8) at end Sep and fell to 9.7 at end Dec. RX And; Maxima occurred on the following dates; Jan 5, 23, Feb 10, Mar 1, 23-, gap until May 23±, Jun 6. 19, Jul, 17, 31, Aug 17 & 23 (peculiar double max), Sep 9, 30, Oct 18, Nov 3, 21, Dec ly 28. Extreme range , period 17 days. DZ And; Observations range and are too few to say more than that the star is certainly variable. R Acl: Fell from 7.0 on Jan 19 to min (11.1) mid May, max (6.5) beginning Oct, down to 9.5 at end Dec. UU Aqls Maxima (11.0) on Jul 17, Oct 16, Dec 6. Observations at minimum range lb. 5-15*5 Underobserved. UW Aql: Possible variations with period about 75 days. Underobserved. R Ari; Rose from 8.9 on Jan 6 to max (8.0) beginning Feb, fell to 8.8 on Mar 3? unobserved until Jul 15, 8.7» then max (8.5) late Jul, min (12.6) mid Nov, up to 10.4 on Dec 22. R Aur; Rose from 10.7 on Jan 7 to max (7.6) mid May; no observations Feb 12 - Apr 21 but there was clearly a hump on the rise at 9.8. Near min (13.1) at end Dec. X Aur; Min (12-.7) late Jan, max (8,3) early Apr, min (13.2Ϊ) mid Jul, max (8.8) beginning Oct, near min (13.2) at end Dec. SS Aur; Maxima Jan 25 (11.0, L), Mar 28 (11.8, S), Aug 10i (11.0±, S), Oct 3± (11.4±, s), Dec 4 (10.8, L). No positive observations May 19 - Aug 11 and if one maximum was missed the period comes to 63 days. CO Aur; Slight irregular variations

7 6 R Boo; Rose from 7.7 on Jan 7 to max (7.0) end Jan, min (12.5) beginning Jun, max (7 A) early Sep, down to 11.7 on Dec 12. S Boo: Rotre from Feb 22, 13.8 to max (9 3) beginning Jul, fell to Oct 13, ϋ Boo: Rose from Jan 5» 11.0 to max (10.6) late Jan, min (12.8) early Apr, max (10.3) early Aug (with secondary max on rise at 10.8), fell to Oct 8, 12.5«V Boos Rose from Jan 7» 9.6 to max (8.0) Jun/Jul, min (9.8) early Oct, up to 8.5 in Dec. VCams Faint for most of the year, min (15-.9) probably in Jim, max (9,1) end Nov, down to 10.0 at end Dec. X Cams Rose from Jan 6, 10.6 to max (7.6) early Feb. min (13A) late Apr, max (8 A) mid Jul, min (13*3) end Sep, max (8.6) late Nov, down to yc7 at end Dec. ZCams Maxima occurred on the following dates: Feb 1, 26, Mar 25, Apr 18, May 19, Jun 13, Jul 5» Aug 1, Sep 3? 30, Oct 20, Nov 9» 25. Extreme range 10A ? period 25 days. The Nov 9 max is followed by fall to only 12.7, rise to only 11.2 on Nov 25, fall to 11.5 and standstill continuing at the end of the year. TW Cam: Variations with mean 'period" 5-3 days? alternate maxima are 0.1 m deeper. Formal (double) period = 86 days. XX 0ami Possible slight fluctuations Apr ~ end Jun. Underobserved mid- S Cas; Fell from Jam 7, 10.3, to min (15.2) end Sep, up to at end Dec o T Cass Fell from Jan 7j to min (12.3) early Mar, max (7.2) end Nov, down to 7.8 on Dec 25. As usual a pronounced hump on the rise. W Cass Rose from 10.3 early Jan to max (9.0) end Apr, near min (11.7) Dec. UV Gas» Probable slight variations A. Gamma Cass Nearly constant all year at Rho Cos-, Ditto at 5-.9, variations not exceeding 0Ψ2, S Ceps Min (11,5) beginning Feb, max (8.7) Oct. 1 Cep Rose from Jan 2, 9.2 to max (5.9) early Jun, min (10.1) early Dec. A secondary max on the rise at 7.7 Omicron Cets Rose from Jan 5j 8.6 to Mar 28, 3.0. Unobserved until JuJL 1^7375, min (9.0) end Nov, at 8,2 at end Dec. This should be the la S t* ΠιοΧΧ to be lost in daylight for several years. R CrBs Fell from 8.0 on Jan 1 to 11.2 on Feb 23, rose to 8.0 on Apr 27, /.0 on Jun 5s 6.5 on Jul 8, 6.05 by Dec. S CrBs Max (6.0) early Feb, min (12.8) mid Sep, up to 7.9 on Dec 25*. T CrBs At minimum, fluctuations ,2, period 120- days. VI CrBt Fell from 8.8 on Jan 18 to min (12.8) mid May, then max (7.8) end Aug, down to 11.9 on Nov 11 (last observation). Fell from 7 A on Jan 2 to min (13.7)early Sep, up to 6.8 on Dec 3 1. S Cygs Rose from on Jan 19 to max (9.9) mid May, fell to mid Aug and remained faint for the rest of the year. ϋ Cygs Rose from 11.6 on -Jan 6 to max (7.8) mid Jul, fell to on Dec 29.

8 W Cvet Fell from 6.2 on Jan 1 to min (7*1) late Feb, then max (6.2) beginning Sep, min (7.2) early Dec, 6.7 on Dec 31. SS Cyg: No maxima were missed although the light-curves of the first four were incomplete: Jan 15 (8,A, S), Feb 26 (8.*+, L or A), Apr 8 (8.5, S), May 6 (8Λ, S), Jun 25 (8Λ, L), Aug 12 (8.5, S). Sep lb (8.5, S), Oct 20 (8.5, S), Nov 20 (8.7, 6), Dec 2b (8.5, L). The magnitude At minimum mas disturbed, a subsidiary rise to 10.5 occurring on Nov 13. BC Cve: Rose from 10Λ5 in Jan to 9.55 in Jun, fell to 9.9 in Sep, probable rise to 9.7 in Nov, down to 10.0 in Dec. B1 Cve: Slow variations pribable. Chi Cyg: Rose from 9.5 on Jan 6 to max (5.2;) early Apr, then min (13.9) end Nov, about 13.2 at end Dec. There was no detectable hump on the rise. AB Dra: Observations are few and often discordant; however maxima, whose magnitudes range , appear to have occurred around Jan 19, Feb 7, 26, Apr 28, Jun 1, 23, Jul 15, 31, Aug 26, Sep *17, Oct 5, 19, Nov l6, Dec *f, 29. Mean interval between maxima is 25 days. Minimum mag » The light-curves of most maxima are peculiar and the variable is probably undergoing an erratic phase with reduced amplitude. Photography with Tri-X. Mr. W.E. Pennell has been securing some valuable results on 7^93 Mon, following the request by J.K. Kalinowski of Indiana University. His photographs have been obtained with Tri-X and a filter equivalent to Wratten o, giving a similar response to the human eye for most stars. This method has been criticised by Dr. Kalinowski and copies of his letters and Mr. Pennell's replies have been sent to the Director since they will be of interest to other astrophotographers. There is not room to publish the correspondence in full, and it is hoped that no important points have been overlooked in the following summary. Dr. K.: "The V filter's effective wavelength is about 5*+80 A and the response is small beyond 6000 A. On the other hand, Tri-X is nearly as sensitive at 6500 A as it is at bluer wavelengths and a W8 filter passes essentially all of this red light. Hence red stars will be recorded on film as brighter than blue stars of the same V magnitude and the error will become larger as one proceeds down the spectral sequence. If you wish to do visual photometry with Tri-X film I urge you to switch to either a Wratten 58 or 61 filter. Unfortunately they transmit less light than the W8, but either is a much better approximation to the V bandpass. Alternatively, to minimise contamination by neighbours you might consider using a red filter, say one that turns on around 6000 A, to utilise only the reddest 500 or 600 A of Tri-X's spectral sensitivity (e.g. a Wratten 25, or similar filter). You would not then be on any photometric system but you could establish your own sequence." W.E.P.: "I believe that for 90$ of the stars in a given field, Tri-X + W8 does what is asked of it - namely to indicate magnitudes to within 0 ¾ - 0?3«Of course this does not equate with professional standards. The whole object is to cut out the cumbersome plate reductions, with short exposure "see at a glance" pictures. Wratten 58 transmits only 28$ of sunlight (compared with an 80$ transmission for Wratten 8) and would be a serious limitation for small apertures. My ata was to iron out the yellow dip in the Tri-X sensitivity curve. Looking at the transmission graph for W8 there is a cut-off at *+600 A, but it is open-ended for red-wavelengths - but the sensitivity of Tri-X falls off very rapidly over 6000 A and disappears completely above 6h-5Q A. 7

9 This is for 35 mm film - it should not be confused with Tri-X Pan Plate Type B which Dr. K. was looking at. It is certainly my intention to try to improve the filter combination. It should be noted that the light yellow filters I use are x if - photographic ones and are not true Wratten filters and possibly do not have the same cut-off at b60q A." Dr. E. * : I would tend to agree that measures of normal stars to within perhaps -t03?3 are probably possible using this filter/film combination. However5 stars with strong emission or very red stars will not be accurately monitored by this technique. People should be aware that the problem does exist and is greatest for very late-type stars. For observers who can afford the additional light-loss a filter better matched to the V bandpass is strongly recommended." V566 Oph. Prof. Kaitchuek of Ball State University, Indiana, is interested in VSS observations of this eclipsing binary and has written to the Directors "I would like to encourage you and your group to continue to observe this system. I was particularly impressed by your 197'+ timing,(s:ee.august Journal). The agreement between this single visual observation and an unpublished photoelectric timing I did that same year is very good.1* This star recently underwent a period change, which was discussed by Saitchuck and Bookmyer in a paper in the AAVSO Journal, but "we both feel that the 0-0 diagram shows so much scatter m the daua points that we can't te3_l exactly what is going on." It is possible that the shape of the light-curve is variable, in which case visual^timings are of not greatly inferior accuracy compared with photoelectric results. However, it is important to get a good run on both falling and rising branches because of the variable's small amplitude. S Per. A paper by Horace A. Smith in the same issue (Vol 3, No 1) of the AAVSO Journal presented the results of a periodogram analysis of this star's light-curve ^9 from AAVSO observations since 1911 and from ail available observations before that date. The result - waves of unequal amplitude and periods 82:5 and 9*+0 days - is almost identical to that obtained, from different observations and by a simplified method cf discussion, in the VSS report in the 1973 June Journal, and confirms that the GOVS data require revision. It is, however',* " clear tnat this star is not fully 'worked out' in view of the many irregularities and the possibility of a very slow variation in mean brightness. VSS programme. Jeremy Bailey writess "Can I suggest two objects as possible additions to the VSS programme. The first is V Sge, a nova like variable which is also an eclipsing binary. The eclipses are well over a magnitude deep when the star is faint (Herbig, G,H., Preston, G.W., Smak, J., and Paczynski, B., Ap. J., ij+l, 617, 1965) and so should easily be'observable visually. The other object is HZ Her (= the X-ray binary Her X-l). This normally shows variations with a period of 1.7 days and a range of about 13-15? interpreted as being due to X-ray heating of one side of the primary by its neutron star companion. However, analysis of patrol plate observations (Jones, C.A., Forman, W., and Liller, W., Ap. J.. 182, L109, 1973) shows that at intervals of around 10 years the star exhibits an 'extended low' state where the X-ray heating is apparently absent and the star is nearly constant at around 15 with only a small amplitude ellipsoidal variation. The transition from 'extended high' to'extended low' has never been observed. It is not known how long the transition would take or when it is likely uo occur, so it would, seem well worth keeping a watch on the star." While it is easy to appreciate hew important observations of these objects could be - indeed they probably have a better claim to our attention...

10 tion than some objects already on our working list - there is a danger that our programme, already large, may become too large for us to be able to make use of the results reported by observers, or for all the stars on the programme to be covered adequately. Perhaps there is a case for dropping more stars from the programme, possibly as tfell as some of those which have been earmarked for inclusion when adequate charts are available. Members may over-estimate the amount of time which the Sections officers are able to spend on their work for the VSS and the amount of money which the BAA is able to spend on publications, so the final decisions must rest with the VSS officers and the BAA Council- but the Director will always, welcome constructive suggestions on ways j.n which the methods, programme and publications of the Section might be improved, and the more interesting can be published in VSS Circulars. Meanwhile, of course, it is essential that observers conform to the methods and programme at present laid down, in the observations they report to the Section. An Apology. The Director regrets that, following his recent move, he has had less time to devote to the Section. The situation should improve towards the end of the year when decorating is finished. In the meantime it is intended to continue unabated the preparation of reports for the Journal, while VSS Circulars will continue to appear, and all correspondence will be dealt with, although sometimes after some delay. There will? however, be a pause in the issue of new charts (except for the Binocular Group), and the new chart catalogue will also be delayed. Members who have requested copies from Mr. Anderson will receive them in due course and need not write again. Overseas visitors. The Director was pleased recently to meet Frank Bateson, Director of the Variable Star Section of the Royal Astronomical Society of New Zealand, and Tom Cragg, of Hale Observatories, a leading member of the AAVSO, both of whom ware recently in England. As well as having a useful exchange of ideas, some agreement was reached on possible further areas for international collaboration. In particular, the VSS will take part in the programme of observation of long-period classical Cepheids (the object of which is to detect period changes which may result from stellar evolution) which is being co-ordinated for the AAVSC by Mr. Cragg. Further details will be given in a forthcoming issue of the Journal, but in the meantime interested members may write to Mr..-Cragg at Hale Observatories,. Mount Wilson, Calif. 91D23.,-U.S^L. 9

11 10 STOP PRESS 8 NOVA CYGNI 1975 Host members will by now know of the discovery by Honda» on 1975 Aug GMAT, of a brilliant nova in Cygnus at about 21 h 10a, ' 0 95^), the brightest in the northern hemisphere since 1934 This area was swept for novae by George Alcock the previous evening, so that it was almost certainly then below sixth magnitude. The magnitude at the time of discovery is reported as 3 During the evening of Aug 29, and on subsequent nights, I received many reports of independent discoveries by our members. My own estimates, reduced according to the sequence given below, showed a possible rise from 2.5 at to 2.2 at ; I was unsure of the reality of this rise but the nova was certainly brighter the following night, Aug 30, when I glimpsed it through cloud at magnitude 1.5 I was clouded out on Aug 31, but observations reported, to me by several members suggest that a fail of some tenths of a magnitude had occurred. I understand that the spectrum was photographed on the night of discovery at Herstmonceux and by Steve Anderson, but no details are known at the time of writing. Observers agree that the colour on Aug 29, 30 and 31 was yellowish, as was to be expected;; the spectrum of a nova at maximum generally resembles that of an F, G or K giant. A chart is hardly necessary at the moment; the following comparison stars may be used as long as the nova remains a naked-eye object. Magnitudes are means of photoelectric V measures given in the US Naval Observatory Catalog, All the stars can be identified in Norton's Star Atlas. Alpha Lyr 0.C4 AO Delta Cyg 2.87 AO?i2 Cyg Alpha Cyg 1.25 A2 Beta Cyg Cyg 4*53 1¾ Gamma Cyg 2,21 F 8 Xi Cyg 3.71 K5 Pi1 Cyg Alpha Cep 2,4 4 A7 Nu Cyg 3.93 AO 60 Cyg Epsilon Cyg 2,46 ICO Rho Cyg G8 Struve 2741 Cyg 5.6I E8 The nova is ideally placed for observation, being circumpolar and currently almost overhead in the evening. It is unusual for the rise of a fast nova (as this apparently is) to bo recorded, and the object should also attract good coverage by our observers during its decline. Its behaviour will be discussed at our Chester meeting on Sep 13, and again at the BAA meeting in London on Oct 29, and I should be grateful if members would send me summaries of their observations, reduced according to the above sequence, shortly before these dates. Full details of observations should, of course, be sent to Doug Saw at the end of the year. HR Lyrae project AS Boo and DY Her being no longer effectively observable, these stars have been replaced by DH Peg and DY Peg. Observations cf AE Boo and DY Her will now be analysed and should be sent to me immediately. Participants in this project will find enclosed charts for DH & DY Peg and AE UMa, with predictions for September and October. Other interested members should write to me. John Isles 19?5 September 1